522 DISCUSSION. 



opinion that Mr. Tillyard's zoocentres were simply areas in which 

 the greatest mutation had occurred. 



Mr. Fletcher pointed out the very great importance of climate 

 as a determining factor; and asked Mr. Tillyard whether he could 

 establish any correlation between his specific contours, and the 

 known facts of rainfall-distribution in Australia. 



Mr. Waterhouse said that faunal regions were very indefinite, 

 and merged into another. He had long ago recognised the essen- 

 tial difference between entogenic and ectogenic groups; the idea 

 was not a new one, but only presented in a new manner. He also 

 pointed out how important it was that depressions or lacunae in the 

 contours should be carefully shown. 



Mr. Darnell Smith gave a summary of the distribution of earth- 

 worms, and finally announced himself as a supporter of Mr. Till- 

 yard's scheme. 



Mr. Mackinnon said that he had succeeded in establishing an 

 entogenic contour for one group of parasitic fungi (Uromyces), but 

 had failed to get any definite result with Puccinia. He objected to 

 the introduction of new names, which only added to the burden of 

 scientific study. He advocated the use of transparencies over pre- 

 pared maps. 



Mr. Maiden laid stress upon the paucity of data for most groups, 

 also on the indefiniteness of species. These would prove grave dif- 

 ficulties in the use of Mr. Tillyard's method. 



Dr. Kesteven claimed that Mr. Tillyard's method did not show 

 all the facts. He objected to the term "archipelagic contour " He 

 instanced, as a case of discontinuity, that a group of rushes 

 occurred in all the waterholes throughout Central Australia ; but as 

 these waterholes were many miles apart, the contour for the group 

 would be a number of small ovals, and would be discontinuous, 

 though not archaic. He also said that one closed oval, within 

 another, did not accurately represent the double distribution of 

 two species, whereas two ovals, cutting one another, did do so. He 

 also asked what was to prevent the species within the highest con- 

 tour-oval being all different from those of the next, and so on, so 

 that with contours 4, 3, 2, 1, no less than ten species would be 

 represented. 



